Nuclear magnetic resonance device

ABSTRACT

A nuclear magnetic resonance apparatus includes a nuclear magnetic resonance device for elucidating atomic configuration and molecular structure of a substance based on a decay signal of induced electromotive force caused by resonance precession of nuclear magnetic moment induced by irradiation of electro-magnetic pulses in an RF region when the substance is exposed to a strong magnetic field, and a vibration isolation mechanism for suppressing vibrations. The vibration isolation mechanism has, as an actuator, an air spring connected to a pressurized air source via an electro-pneumatic converter and acting to exert a force for vibration isolation on the nuclear magnetic resonance device. The vibration isolation mechanism is capable of active vibration isolation, and disposed away from the nuclear magnetic resonance device by such a distance that the electro-pneumatic converter never incurs any malfunctions or operating failures under influence of a magnetic field generated by the nuclear magnetic resonance device.

TECHNICAL FIELD

The present invention relates to a nuclear magnetic resonance apparatusequipped with a vibration isolation mechanism.

BACKGROUND ART

Conventionally, a nuclear magnetic resonance apparatus has been knownwhich comprises a nuclear magnetic resonance means for elucidating anatom configuration and a molecular structure of a substance based on adecay signal of induced electromotive force caused by resonanceprecession of nuclear magnetic moment induced by irradiation ofelectro-magnetic pulses in an RF region when a substance is exposed to astrong magnetic field, and a vibration isolation mechanism forsuppressing vibration of this nuclear magnetic resonance means (seee.g., Japanese Patent Laid-Open publication No. 2001-145611, paragraph[0011], FIG. 1).

A vibration isolation mechanism itself of an active type using an airspring has also been known (see, e.g., “6DOF microvibration ControlSystem using Air Actuators (Experimental Study on Vibration Isolationand Damping Performance)”, Yasutaka TAGAWA and four others, Proceedingsof Dynamics and Design Conference'94, JSME, No. 940-26(II), pp. 544,1994.07).

In a vibration isolation mechanism constituted by a spring-mass system(a surface plate and a mounted component), i.e. a vibration isolationmechanism of the passive type, vibration is amplified by resonance at anatural frequency of the spring-mass system. In contrast to this, thevibration isolation mechanism of the active type is a vibrationisolation mechanism comprising a means for detecting a vibration stateor a displacement state of a component to be isolated from vibration,namely, a controlled object, a control means for outputting a signal tocancel the vibration of the controlled object based on a detected signalby the detection means, an actuator (e.g., air spring, piezoelectriclaminate) for exerting a force on the controlled object to cancel thevibration by receiving a signal from the control means, and the like,whereby feedback control is performed to avoid the resonance at thenatural frequency and to suppress the amplification of the vibration bythe resonance. This active type vibration isolation mechanism has becomeindispensable particularly for precision mechanical equipment adverselyaffected easily even by micro-vibration.

In the case of the apparatus described in the Japanese Patent Laid-Openpublication No. 2001-145611 in which a passive-type vibration isolationmechanism is employed as the vibration isolation mechanism, since avibration is amplified at around the natural frequency as describedabove, the vibration isolation mechanism is unsuitable for vibrationisolation of a nuclear magnetic resonance apparatus which is a precisionmeasuring instrument. That is, in the case of the nuclear magneticresonance apparatus using the passive type vibration mechanism, sincethe vibration of the apparatus causes side band noise in a nuclearmagnetic spectrum responsive to a frequency of the vibration, such aproblem arises that precision measurement can not be performed by theapparatus.

On the other hand, the aforementioned active type vibration isolationmechanism employs such a constituent element as a servo valve or a servoacceleration sensor which may lead to malfunctions or operating failuresunder the influence of an external strong magnetic field. Therefore,even if a nuclear magnetic resonance apparatus formed by applying thisactive type vibration isolation mechanism of the conventional type tothe nuclear magnetic resonance means which is a source of a strongmagnetic field, such a problem arises that the vibration isolationmechanism does not operate normally, with the result that it becomesimpossible to perform precision measurement also by this nuclearmagnetic resonance apparatus as in the foregoing case.

It is an object of the present invention to provide a nuclear magneticresonance apparatus which solves the above-described problems of theprior art and which allows the vibration isolation mechanism to fullyexert an inherent performance even under a strong magnetic field,thereby suppressing vibration and enabling precision measurement.

DISCLOSURE OF THE INVENTION

In order to achieve the above object, according to a first aspect of thepresent invention, there is provided a nuclear magnetic resonanceapparatus comprising: a nuclear magnetic resonance means for elucidatingan atom configuration and a molecular structure of a substance based ona decay signal of induced electromotive force caused by resonanceprecession of nuclear magnetic moment induced by irradiation ofelectro-magnetic pulses in an RF region when a substance is exposed to astrong magnetic field; and a vibration isolation mechanism forsuppressing vibration of this nuclear magnetic resonance means, whereinthe vibration isolation mechanism has an air spring as an actuator, theair spring being connected to a pressurized air source via anelectro-pneumatic converter and acting to exert a force for vibrationisolation on the nuclear magnetic resonance means, and the vibrationisolation mechanism is formed so as to be capable of active vibrationisolation, and disposed away from the nuclear magnetic resonance meansby such a distance that the electro-pneumatic converter never incurs anymalfunctions or operating failures under influence of a magnetic fieldgenerated by the nuclear magnetic resonance means.

With this constitution, the leak magnetism from the nuclear magneticresonance means is weakened in the vicinity of the electro-pneumaticconverter, thus producing effects that the inherent performance of thevibration isolation mechanism can be fully obtained even under a strongmagnetic field, the vibration is suppressed without incurringamplification of the vibration due to the resonance at the naturalfrequency, and that precision measurement can be performed.

According to a second aspect of the present invention, there is provideda nuclear magnetic resonance apparatus comprising: a nuclear magneticresonance means for elucidating an atom configuration and a molecularstructure of a substance based on a decay signal of inducedelectromotive force caused by resonance precession of nuclear magneticmoment induced by irradiation of electro-magnetic pulses in an RF regionwhen a substance is exposed to a strong magnetic field; and a vibrationisolation mechanism for suppressing vibration of this nuclear magneticresonance means, wherein the vibration isolation mechanism has an airspring as an actuator, the air spring being connected to a pressurizedair source via an electro-pneumatic converter and acting to exert aforce for vibration isolation on the nuclear magnetic resonance means,and the vibration isolation mechanism is formed so as to be capable ofactive vibration isolation, and the electro-pneumatic converter isaccompanied by a means for decaying a magnetic field leaking outsidefrom the nuclear magnetic resonance means and is disposed at such aposition that the leakage magnetic field is decayed.

With this constitution, the leakage magnetic field from the nuclearmagnetic resonance means is weakened by the means for decaying themagnetic field, and the electro-pneumatic converter is protected fromthis leakage magnetic field, thus producing effects that the inherentperformance of the vibration isolation mechanism can be fully obtainedeven under a strong magnetic field, the vibration is suppressed withoutincurring amplification of the vibration due to the resonance at thenatural frequency, and that precision measurement can be performed.

According to a third aspect of the present invention, there is provideda nuclear magnetic resonance apparatus comprising: a nuclear magneticresonance means for elucidating an atom configuration and a molecularstructure of a substance based on a decay signal of inducedelectromotive force caused by resonance precession of nuclear magneticmoment induced by irradiation of electro-magnetic pulses in an RF regionwhen a substance is exposed to a strong magnetic field; and a vibrationisolation mechanism for suppressing vibration of this nuclear magneticresonance means, wherein the vibration isolation mechanism has an airspring as an actuator, the air spring being connected to a pressurizedair source via an electro-pneumatic converter and acting to exert aforce for vibration isolation on the nuclear magnetic resonance means,and the vibration isolation mechanism is formed so as to be capable ofactive vibration isolation, and the electro-pneumatic converter isdisposed so as to generate a driving magnetic field perpendicular to adirection of a leakage flux from the nuclear magnetic resonance means.

With this constitution, a driven portion within the electro-pneumaticconverter operates normally without being affected by the magnetic fielddue to the nuclear magnetic resonance means, thus producing effects thatthe inherent performance of the vibration isolation mechanism can befully obtained even under a strong magnetic field, the vibration issuppressed without incurring amplification of the vibration due to theresonance at the natural frequency, and that precision measurement canbe performed.

According to a fourth aspect of the present invention, in addition tothe constitution of any one of the first to third aspects, the airspring and piping system are formed of nonmagnetic material.

With this constitution, in addition to the effects of any one of thefirst to third aspects of the invention, there are produced effects thatthe influence of the magnetic field due to the nuclear magneticresonance means to which the electro-pneumatic converter is subject isfurther weakened, and that the reliability of the apparatus can befurther improved.

According to a fifth aspect of the present invention, in addition to theconstitution of any one of the first to fourth aspects, a control meansof the vibration isolation mechanism performs such a control thatcontrolling pressure generated by the electro-pneumatic converter islowered at around a fluid resonance frequency so as to suppressoccurrence of fluid resonance between the air spring and theelectro-pneumatic converter.

With this constitution, in addition to the effects of any one of thefirst to fourth aspects of the invention, there are produced effectsthat the active vibration isolation can be fulfilled even when thecontrol pressure by the electro-pneumatic converter fluctuates at aroundthe fluid resonance frequency, as in the case of other frequencies, andthat the reliability of the apparatus can be further improved.

According to a sixth aspect of the present invention, in addition to theconstitution of any one of the first to fifth aspects, the vibrationisolation mechanism includes a piezoelectric acceleration sensor as avibration detection means.

With this constitution, in addition to the effects of any one of thefirst to fifth aspects of the invention, there is produced an effectthat the vibration state of the nuclear magnetic resonance means can bedetected without being affected by a strong magnetic field.

According to the seventh aspect of the present invention, in addition tothe constitution of any one of the first to fifth aspects, the vibrationisolation mechanism includes a servo acceleration sensor as a vibrationdetection means, and this servo acceleration sensor includes a means fordecaying a magnetic field leaking outside from the nuclear magneticresonance means and is disposed at such a position that the leakagemagnetic field is decayed.

With this constitution, in addition to the effects of any one of thefirst to fifth aspects of the invention, there is produced an effectthat a servo acceleration sensor most suitable for micro-vibrationmeasurement becomes applicable also to the detection of the vibrationstate of the nuclear magnetic resonance means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the overall construction of a nuclearmagnetic resonance apparatus according to the present invention.

FIG. 2 is a graph showing vibration isolation characteristics of thenuclear magnetic resonance apparatus shown in FIG. 1 and a nuclearmagnetic resonance apparatus using a passive type vibration isolationmechanism.

FIG. 3 shows another configuration for supporting a nuclear magneticresonance means of the nuclear magnetic resonance apparatus shown inFIG. 1.

FIG. 4 shows still another configuration for supporting the nuclearmagnetic resonance means of the nuclear magnetic resonance apparatusshown in FIG. 1.

FIG. 5 is a block diagram showing the overall construction of anothernuclear magnetic resonance apparatus according to the present inventionand its state of application.

FIG. 6 is a sectional view of an electro-pneumatic converter whichgenerates a driving magnetic field perpendicular to the direction of aleakage flux from the nuclear magnetic resonance means.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention are described withreference to the drawings.

FIG. 1 shows a nuclear magnetic resonance apparatus 1A according to thepresent invention, and this nuclear magnetic resonance apparatus 1A iscomprised of a nuclear magnetic resonance means 2 and a vibrationisolation mechanism 3.

The nuclear magnetic resonance means 2, which is a well known oneincluding a magnetic resonance imaging means, is intended to elucidatean atomic configuration and a molecular structure of a substance basedon a decay signal of induced electromotive force caused by resonanceprecession of nuclear magnetic moment induced by irradiation ofelectro-magnetic pulses in an RF region when the substance is exposed toa strong magnetic field.

The vibration isolation mechanism 3, which is provided for activevibration isolation of the nuclear magnetic resonance means 2, iscomprised of an air spring 11 as an actuator and a control system 12including vibration sensors S₁, S₂, displacement sensor S₃ or the likeas detection means.

The air spring 11 is interposed between a base B disposed on aninstallation part P adjustably in horizontal level and the nuclearmagnetic resonance means 2 which is a vibration controlled object by thevibration isolation mechanism 3. In other words, the nuclear magneticresonance means 2 is supported horizontally on the base B via the airspring 11.

In addition to the aforementioned detection means (vibration sensors S₁,S₂, displacement sensor S₃), the control system 12 is provided with aninstallation-part vibration controller 21, a controlled-object vibrationcontroller 22, a displacement controller 23, a driver 24 and anelectro-pneumatic converter 25.

The vibration sensor S₁ detects a vibration state of the installationpart P, and a signal showing the detected vibration state is inputted tothe installation-part vibration controller 21. The vibration sensor S₂detects a vibration state of the nuclear magnetic resonance means 2, anda signal showing the detected vibration state is inputted to an adder 31and, inputted to the controlled-object vibration controller 22 with itspositive/negative polarity inverted. The displacement sensor S₃ detectsa relative displacement amount of the nuclear magnetic resonance means 2to the installation part P, and a signal showing the displacement amountis inputted to an adder 32 as a negative signal. In the adder 32, avalue of desired lifting amount of the nuclear magnetic resonance means2 from the installation part P has been inputted as a target value, anda signal showing a difference between this desired lifting amount andthe relative displacement amount is inputted from the adder 32 to thedisplacement controller 23.

The vibration sensors S₁, S₂ are basically seismic-system's onescomposed of, for example, piezoelectric elements and nonmagnetic masses,and preferably piezoelectric acceleration sensors that are not affectedby any magnetic field. Alternatively, the vibration sensors S₁, S₂ maybe servo acceleration sensors accompanied by a means for decaying themagnetic field leaking outside from the nuclear magnetic resonance means2, and disposed at such a position that the leakage magnetic field isdecayed. Although the servo acceleration sensors are affected by themagnetic field because each of them includes an electro-magnetic driverportion of voice coil type, the servo acceleration sensors are superiorin micro-vibration resolution characteristics to the piezoelectricacceleration sensors. The means for decaying the magnetic field will bedescribed later.

Furthermore, preferably, the displacement sensor S₃ is, for example, aneddy-current type displacement sensor or a laser displacement meter.

From each of the installation-part vibration controller 21, thecontrol-object vibration controller 22 and the displacement controller23, a control signal for canceling each of their input signals isinputted to an adder 33, and a control signal resulting from summing upthese three control signals is inputted from the adder 33 to the driver24.

The air spring 11 is connected to a pressurized air source 34 via theelectro-pneumatic converter 25 disposed at a position distant from thenuclear magnetic resonance means 2 by such a distance that the airspring 11 never incurs any malfunctions or operating failures under theinfluence of a magnetic field generated by the nuclear magneticresonance means 2, more specifically, at a position where the magneticflux density becomes about 5 gauss or less, and the electro-pneumaticconverter 25 operates based on a driving signal from the driver 24, towhich the control signal resulting from summing up the three controlsignal has been inputted. That is, the electro-pneumatic converter 25promptly responds to the aforementioned two vibration states anddisplacement amount, so as to continuously adjust the pressurized airamount inside the air spring 11, to thereby perform vibration isolationof the nuclear magnetic resonance means 2.

As the electro-pneumatic converter 25, for example, an electro-pneumaticservo valve whose flapper is operated by magnet may be used.

FIG. 2 shows, by using the vibration state of the installation part P asa reference, vibration isolation characteristics of the nuclear magneticresonance apparatus 1A according to the present invention, in which theabove-described active type vibration isolation mechanism is applied tothe nuclear magnetic resonance means 2 generating a strong magneticfield, as well as vibration isolation characteristics of a conventionalnuclear magnetic resonance apparatus in which a passive type vibrationisolation mechanism formed of a spring-mass system is applied to thenuclear magnetic resonance means 2. In FIG. 2, the horizontal axisrepresents the vibration frequency (Hz) expressed in the logarithmicscale, F₀ represents a first order natural frequency, and the verticalaxis represents the amplification factor [dB] of vibrations of thenuclear magnetic resonance means 2 when the vibration level of theinstallation part P is taken as a reference (=0), and a curve Icorresponds to a case of the nuclear magnetic resonance apparatus 1Aunder the active vibration isolation and a curve II corresponds to thecase of the conventional nuclear magnetic resonance apparatus under thepassive vibration isolation. As can be seen from this FIG. 2, in theregion higher than the natural frequency F₀, both the nuclear magneticresonance apparatus 1A and the conventional nuclear magnetic resonanceapparatus show similarly good damping characteristics. At around thenatural frequency F₀, the conventional nuclear magnetic resonanceapparatus amplifies the vibrations, while the nuclear magnetic resonanceapparatus 1A shows good damping characteristics.

The present invention is not limited to the one in which the nuclearmagnetic resonance means 2 is supported as shown in FIG. 1, but includesthose in which the nuclear magnetic resonance means 2 is supported insuch a manner as shown in FIG. 3 or 4, where components of FIGS. 3 and 4common to those of FIG. 1 are designated by like reference numerals.

It is noted that the nuclear magnetic resonance means 2 shown in FIG. 3has its upper portion supported horizontally on the base B via the airspring 11, while the nuclear magnetic resonance means 2 shown in FIG. 4has its side portion supported horizontally on the surface plate B viathe air spring 11.

FIG. 5 shows another nuclear magnetic resonance apparatus 1B accordingto the present invention, which is substantially similar to theabove-described nuclear magnetic resonance apparatus 1A except that anactive type vibration isolation mechanism 4 is applied instead of thevibration isolation mechanism 3, where components common to each otherare designated by like reference numerals and their description omitted.

In this nuclear magnetic resonance apparatus 1B, an electro-pneumaticconverter 25 is housed within a magnetic shield box 41, which is anexample of the means for decaying the magnetic field leaking outsidefrom the nuclear magnetic resonance apparatus 1B. Therefore, thiselectro-pneumatic converter 25 is not necessarily located away from thenuclear magnetic resonance means 2 as in the case of the nuclearmagnetic resonance apparatus 1A.

In this nuclear magnetic resonance apparatus 1B, a magnetic field as adisturbance to the electro-pneumatic converter 25 is interrupted by themagnetic shield box 41, by which the influence of the external magneticfield on the electro-pneumatic converter 25 is eliminated. As a result,normal operation of the electro-pneumatic converter 25 is ensured. Thismagnetic shield box 41 is preferably formed of a material having highmagnetic permeability such as permalloy or pure iron.

As a means for decaying the magnetic field, for example, a permanentmagnet or a magnetism generation coil may be used instead of or inaddition to the above magnetic shield box.

In this case, by a magnetic field generated from the permanent magnet ormagnetism generation coil, a leakage magnetic field from the nuclearmagnetic resonance apparatus 1B incident on the electro-pneumaticconverter 25 is degaussed, or the incidence amount of the leakagemagnetic field in a sensitive direction of the electro-pneumaticconverter 25 is decreased.

In addition, also in this nuclear magnetic resonance apparatus 1B,needless to say, piezoelectric acceleration sensors or servoacceleration sensors may be applied as the vibration sensors S₁, S₂, andan eddy-current type displacement sensor or a laser displacement gaugemay be applied as the displacement sensor S₃, as described above.

The present invention is not limited to the above embodiments. That is,the electro-pneumatic converter 25 does not necessarily need to bedisposed away from the nuclear magnetic resonance means 2 as in the caseof the nuclear magnetic resonance apparatus 1A, and further theelectro-pneumatic converter 25 does not necessarily need to be disposedwithin the magnetic shield box 41 as in the case of the nuclear magneticresonance apparatus 1B. Instead, as shown in FIG. 6, theelectro-pneumatic converter 25 may be so disposed as to generate adriving magnetic field perpendicular to the direction of a leakage fluxfrom the nuclear magnetic resonance means 2, and the present inventionincludes a nuclear magnetic resonance apparatus of such construction aswell. It is noted that in FIG. 6, reference numeral 51 denotes a flapperand 52 denotes a torque-motor driving magnetic pole.

By the arrangement that the electro-pneumatic converter 25 is sodisposed as to generate a driving magnetic field perpendicular to thedirection of a leakage flux from the nuclear magnetic resonance means 2as shown above, the influence of the magnetic field due to the nuclearmagnetic resonance means 2 to which the electro-pneumatic converter 25is subject is weakened.

Also, in each of the above-described apparatuses, the air spring 11 andthe piping system are preferably formed of nonmagnetic material. Bydoing so, the influence of the magnetic field due to the nuclearmagnetic resonance means 2 to which the electro-pneumatic converter 25is subject is further weakened.

Further, in each of the above-described apparatuses, in order tosuppress fluid resonance that occurs between the air spring 11 and theelectro-pneumatic converter 25, it is preferable that the controllingpressure generated by the electro-pneumatic converter 25 is lowered ataround the fluid resonance frequency. In execution of the pressurecontrol in the air spring 11 by means of the servo valve in theelectro-pneumatic converter 25, when pressurized fluid is subjected to avolumetric change through the piping system extending from thepressurized air source 34, there would occur internal resonance whichwould cause the fluid to resonate, resulting in deterioration of thecontrol characteristics. However, by correcting the controlling pressuregenerated by the electro-pneumatic converter 25 as described above, itbecomes possible to fulfill the active vibration isolation even when thecontrolling pressure in the electro-pneumatic converter 25 fluctuates ataround the fluid resonance frequency, as in the case of otherfrequencies.

In addition, in the feedback loop, a resonance eliminating filter may beinterposed, for example, between the adder 33 and the driver 24.

1. A nuclear magnetic resonance apparatus comprising: nuclear magneticresonance means for elucidating atomic configuration and molecularstructure of a substance based on a decay signal of inducedelectromotive force caused by resonance precession of nuclear magneticmoment induced by irradiation of electro-magnetic pulses in an RF regionwhen the substance is exposed to a strong magnetic field; and avibration isolation mechanism for suppressing vibration of this nuclearmagnetic resonance means, wherein the vibration isolation mechanism hasan air spring as an actuator, the air spring being connected to apressurized air source via an electro-pneumatic converter and acting toexert a force for vibration isolation on the nuclear magnetic resonancemeans, and the vibration isolation mechanism is formed so as to becapable of active vibration isolation, and disposed away from thenuclear magnetic resonance means by such a distance that theelectro-pneumatic converter never incurs any malfunctions or operatingfailures under influence of a magnetic field generated by the nuclearmagnetic resonance means, and wherein a control means in the vibrationisolation mechanism performs such a control that controlling pressuregenerated by the electro-pneumatic converter is lowered at around afluid resonance frequency so as to suppress occurrence of fluidresonance between the air spring and the electro-pneumatic converter. 2.The nuclear magnetic resonance apparatus as claimed in claim 1, whereinthe air spring and piping system are formed of nonmagnetic material. 3.The nuclear magnetic resonance apparatus as claimed in claim 2, whereinthe vibration isolation mechanism includes a piezoelectric accelerationsensor as a vibration detection means.
 4. The nuclear magnetic resonanceapparatus as claimed in claim 2, wherein the vibration isolationmechanism includes a servo acceleration sensor as a vibration detectionmeans, and this servo acceleration sensor includes a means for decayinga magnetic field leaking outside from the nuclear magnetic resonancemeans and is disposed at such a position that the leakage magnetic fieldis decayed.
 5. The nuclear magnetic resonance apparatus as claimed inclaim 1, wherein the vibration isolation mechanism includes apiezoelectric acceleration sensor as a vibration detection means.
 6. Thenuclear magnetic resonance apparatus as claimed in claim 1, wherein thevibration isolation mechanism includes a servo acceleration sensor as avibration detection means, and this servo acceleration sensor includes ameans for decaying a magnetic field leaking outside from the nuclearmagnetic resonance means and is disposed at such a position that theleakage magnetic field is decayed.
 7. A nuclear magnetic resonanceapparatus comprising: a nuclear magnetic resonance means for elucidatingatomic configuration and molecular structure of a substance based on adecay signal of induced electromotive force caused by resonanceprecession of nuclear magnetic moment induced by irradiation ofelectro-magnetic pulses in an RF region when the substance is exposed toa strong magnetic field; and a vibration isolation mechanism forsuppressing vibration of this nuclear magnetic resonance means, whereinthe vibration isolation mechanism has an air spring as an actuator, theair spring being connected to a pressurized air source via anelectro-pneumatic converter and acting to exert a force for vibrationisolation on the nuclear magnetic resonance means, and the vibrationisolation mechanism is formed so as to be capable of active vibrationisolation, and the electro-pneumatic converter is accompanied by a meansfor decaying a magnetic field leaking outside from the nuclear magneticresonance means and is disposed at such a position that the leakagemagnetic field is decayed, and wherein a control means in the vibrationisolation mechanism performs such a control that controlling pressuregenerated by the electro-pneumatic converter is lowered at around afluid resonance frequency so as to suppress occurrence of fluidresonance between the air spring and the electro-pneumatic converter. 8.The nuclear magnetic resonance apparatus as claimed in claim 7, whereinthe air spring and piping system are formed of nonmagnetic material. 9.The nuclear magnetic resonance apparatus as claimed in claim 7, whereinthe vibration isolation mechanism includes a piezoelectric accelerationsensor as a vibration detection means.
 10. The nuclear magneticresonance apparatus as claimed in claim 7, wherein the vibrationisolation mechanism includes a servo acceleration sensor as a vibrationdetection means, and this servo acceleration sensor includes a means fordecaying a magnetic field leaking outside from the nuclear magneticresonance means and is disposed at such a position that the leakagemagnetic field is decayed.
 11. A nuclear magnetic resonance apparatuscomprising: a nuclear magnetic resonance means for elucidating atomicconfiguration and molecular structure of a substance based on a decaysignal of induced electromotive force caused by resonance precession ofnuclear magnetic moment induced by irradiation of electro-magneticpulses in an RF region when the substance is exposed to a strongmagnetic field; and a vibration isolation mechanism for suppressingvibration of this nuclear magnetic resonance means, wherein thevibration isolation mechanism has an air spring as an actuator, the airspring being connected to a pressurized air source via anelectro-pneumatic converter and acting to exert a force for vibrationisolation on the nuclear magnetic resonance means, and the vibrationisolation mechanism is formed so as to be capable of active vibrationisolation, and the electro-pneumatic converter is disposed so as togenerate a driving magnetic field perpendicular to a direction of aleakage flux from the nuclear magnetic resonance means.
 12. The nuclearmagnetic resonance apparatus as claimed in claim 11, wherein the airspring and piping system are formed of nonmagnetic material.
 13. Thenuclear magnetic resonance apparatus as claimed in claim 11, wherein acontrol means in the vibration isolation mechanism performs such acontrol that controlling pressure generated by the electro-pneumaticconverter is lowered at around a fluid resonance frequency so as tosuppress occurrence of fluid resonance between the air spring and theelectro-pneumatic converter.
 14. The nuclear magnetic resonanceapparatus as claimed in claim 11, wherein the vibration isolationmechanism includes a piezoelectric acceleration sensor as a vibrationdetection means.
 15. The nuclear magnetic resonance apparatus as claimedin claim 11, wherein the vibration isolation mechanism includes a servoacceleration sensor as a vibration detection means, and this servoacceleration sensor includes a means for decaying a magnetic fieldleaking outside from the nuclear magnetic resonance means and isdisposed at such a position that the leakage magnetic field is decayed.